Door knob



FIG. 1 is a perspective view of a door knob showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a top view thereof, the bottom view being a mirror image; and,

FIG. 5 is a right side view thereof, the left side view being a mirror image.

The broken lines in the Figures are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a door knob, as shown and described. 